Filter
Top Products
376
6-4 I/O Response Time
The I/O response time is the time it takes for the PC to output a control signal
after it has received an input signal. The time it takes to respond depends on the
cycle time and when the CPU Unit receives the input signal relative to the input
refresh period.
The minimum and maximum I/O response time calculations described below
are for where IR 00000 is the input bit that receives the signal and IR 00200 is the
output bit corresponding to the desired output point.
00000
00200
6-4-1 Basic Systems
The PC responds most quickly when it receives an input signal just prior to the
I/O refresh period in the cycle. Once the input bit corresponding to the signal has
been turned ON, the program will have to be executed once to turn ON the out-
put bit for the desired output signal and then the I/O refresh operation would
have to be repeated to refresh the output bit. The I/O response time in this case
is thus found by adding the input ON-delay time, the cycle time, and the output
ON-delay time. This situation is illustrated below.
Cycle time
Input
signal
Output
signal
Cycle
Cycle time
I/O refresh
I/O response time
Output ON delay
Input
ON delay
Instruction
execution
Instruction
execution
Instruction
execution
CPU Unit reads
input signal
Minimum I/O response time =
Input ON delay + Cycle time + Output ON delay
Minimum I/O Response
Time
I/O Response Time Section 6-4